torsion-2

• Enlarged ovary (>5 cm maximum diameter) with rounded/spherical morphology and central edema
• Ovary shifted toward midline anterior or posterior to uterus, with uterine deviation toward the torsed side
• Twisted vascular pedicle appearing as a 'whirlpool' structure between uterus and ovary

• T1 weighted imaging may demonstrate a thin rim of high signal intensity (methemoglobin) indicating hemorrhage within the torsed ovary.
• T2 weighted imaging often shows low signal intensity due to interstitial hemorrhage and edema, with follicles displaced peripherally by central stromal edema.
• T1 post-gadolinium imaging reveals reduced or absent contrast enhancement of the torsed ovary, reflecting vascular compromise and ischemia.
• The torsed ovary demonstrates edematous swelling with maximum diameter typically >5 cm (89% sensitive), often with a more spherical configuration than the normal bean-shaped ovary.
• Distension of the fallopian tube on the affected side may be present, indicating tube involvement in the torsion.
• Free peritoneal fluid may be visualized, reflecting the acute inflammatory process and potential hemorrhage.
• The characteristic 'whirlpool' sign shows layered twisting of the fallopian tube, mesosalpinx, and vascular pedicle between the uterus and ovary.
• Associated ovarian mass or cyst (corpus luteum, teratoma, or functional cyst) is present in >85% of cases and may be the nidus for torsion.

• Ectopic pregnancy: positive beta HCG and characteristic gestational sac location; ovary typically normal size without edema.
• Ruptured ovarian cyst: abrupt midcycle pain with free fluid/hemoperitoneum but ovary returns to normal size without persistent edema.
• Pelvic inflammatory disease: more indolent disease course with bilateral salpingitis and endometritis; ovaries normal size.
• Massive ovarian edema from malignant lymphatic obstruction: lack of torsion history and absent whirlpool sign; typically bilateral.
• Degenerating pedunculated leiomyoma: uterine location with heterogeneous signal; no ovarian enlargement or whirlpool sign.
• Appendicitis: inflamed appendix visualized separately; ovaries normal without edema or displacement.

• The diagnosis of adnexal torsion is commonly missed clinically, leading to delayed surgery and increased risk of ovarian infarction within hours of onset.
• Venous and lymphatic obstruction from twisting causes central ovarian edema that further compromises arterial inflow, creating a self-perpetuating cycle of ischemia.
• Over 85% of torsion cases are associated with ovarian enlargement from a mass or cyst; corpus luteum and mature cystic teratomas are the most common predisposing lesions.
• Hemorrhagic infarction can develop rapidly, and imaging delay allows progression from viable (non-friable, blue/black appearance) to necrotic ovary.
• The presence of blood flow on Doppler does not exclude torsion, while absence of flow is highly specific but may not be readily apparent on MRI.
• An ovarian mass presenting acutely with severe pain is suspicious for torsion, as masses are rarely painful unless complicated by torsion, rupture, or hemorrhage.

In whole-body screening MRI, note any enlarged ovary (>5 cm) with central edema and rounded shape; if acute symptoms are present, describe the whirlpool sign and degree of enhancement to alert clinicians to possible torsion requiring urgent surgery.

• Misinterpreting central edema and follicular displacement as a primary ovarian mass rather than recognizing this as the hallmark sign of torsion.
• Assuming normal or preserved Doppler flow excludes torsion; venous obstruction can occur with partially preserved arterial flow.
• Failing to recognize the whirlpool sign due to lack of awareness of its appearance; it is specific but requires careful inspection of the vascular pedicle.
• Attributing an enlarged, edematous ovary with an associated mass solely to the mass effect without considering torsion as a complication, especially in the setting of acute pain.